1. Field of the Invention
The invention relates to novel pyrido[2,3-b]pyrazine derivatives, to processes of manufacturing and use thereof, in particular as medicaments for the modulation of misdirected cellular signal transduction processes, such as modulation of tyrosine kinases, serine/threonine kinases and/or lipid kinases and for the treatment or prophylaxis of malignant or benign oncoses and other disorders based on pathological cell proliferation, for example restenosis, psoriasis, arteriosclerosis and cirrhosis of the liver.
2. Description of Related Art
The activation of protein kinases is a central event in cellular signal transduction processes. Aberrant kinase activation is observed in various pathological states. Targeted inhibition of kinases is therefore a fundamental therapeutic aim.
The phosphorylation of proteins is generally initiated by extracellular signals and represents a universal mechanism for controlling various cellular events, for example metabolic processes, cell growth, cell migration, cell differentiation, membrane trans-port and apoptosis. The kinase protein family is responsible for protein phosphorylation. These enzymes catalyse transfer of phosphate to specific substrate proteins. Based on the substrate specificity, the kinases are divided into three main classes, tyrosine kinases, serine/threonine kinases and lipid kinases. Both receptor tyrosine kinases and cytoplasmic tyrosine, serine/threonine and lipid kinases are important proteins in cellular signal transduction. Overexpression or overactivation of these proteins plays an important part in disorders based on pathological cell proliferations. These include metabolic disorders, disorders of the connective tissue and of the blood vessels, and malignant and benign oncoses. In tumor initiation and development they frequently occur as oncogens, i.e. as aberrant, constitutively active kinase proteins. The consequences of this excessive kinase activation are, for example, uncontrolled cell growth and reduced cell death. Stimulation of tumor-induced growth factors may also be the cause of overstimulation of kinases. The development of kinase modulators is therefore of particular interest for all pathogenic processes influenced by kinases.
Ras-Raf-Mek-Erk and PI3K-Akt signal transduction cascades play a central role in cell growth, cell proliferation, apoptosis, adhesion, migration and glucose metabolism. Thus, the fundamental involvement in the pathogenesis of disorders such as cancer, neurodegeneration and inflammatory disorders has been demonstrated both for ras-Raf-Mek-Erk and for PI3K-Akt signaling pathway. Therefore, the individual components of these signal cascades constitute important therapeutic points of attack for the intervention in the various disease processes (Weinstein-Oppenheimer C R et al., Pharmacol Ther. 2000, 88(3):229-279, Chang F et al., Leukemia 2003, 17(3):590-603; Chang F et al., Leukemia 2003, 17(7):1263-1293; Katso R et al., Annu Rev Cell Dev Biol. 2001, 17:615-675; and Lu Y et al., Rev Clin Exp Hematol. 2003, 7(2):205-228; Hennessy B T et al., Nat Rev Drug Discov 2005, 4, 988-1004).
In the following, the molecular and biochemical properties of the two signaling pathways are first described separately.
A multitude of growth factors, cytokines and oncogens transduce their growth-promoting signals via the activation of G-protein-coupled ras, which leads to the activation of serine-threonine kinase Raf and to the activation of mitogen-activated protein kinase kinase 1 and 2 (MAPKK1/2 or Mek1/2), and results in the phosphorylation and activation of MAPK 1 and 2—also known as extracellular signal-regulated kinase (Erk1 and 2). Compared to other signaling pathways, ras-Raf-Mek-Erk signaling pathway combines a large number of proto-oncogenes, including ligands, tyrosine kinase receptors, G proteins, kinases and nuclear transcription factors. Tyrosine-kinases, for example EGFR (Mendelsohn J et al., Oncogene. 2000, 19(56):6550-6565) mediate, in the course of tumor process, caused by overexpression and mutation, frequently constitutively active signals to downstream ras-Raf-Mek-Erk signaling pathway. Ras is mutated in 30% of all human tumors (Khleif S N et al., J Immunother. 1999, 22(2):155-165; Marshall C, Curr Opin Cell Biol. 1999, 11(6):732-736) the highest incidence at 90% being in pancreas carcinomas (Friess H et al., J Mol. Med. 1996, 74(1):35-42; Sirivatanauksorn V et al., Langenbecks Arch Surg. 1998, 383(2):105-115). As for c-Raf, deregulated expression and/or activation have been described in various tumors (Hoshino R et al., Oncogene 1999, 18(3):813-822; McPhillips F et al., Br J Cancer 2001, 85(11):1753-1758). B-Raf point mutants have been detected in 66% of all human malignant melanomas, 14% of ovarian carcinomas and 12% of colon carcinomas (Davies H et al., Nature 2002, 417(6892):949-954). It is therefore not surprising that Erk1/2 is involved at primary stage in many cellular processes, such as cell growth, cell proliferation and cell differentiation (Lewis T S et al., Adv Cancer Res. 1998, 74:49-139; Chang F et al., Leukemia 2003, 17(3):590-603; Chang F et al., Leukemia 2003, 17(7):1263-1293).
In addition, members of Raf kinases also have Mek-Erk-independent, anti-apoptotic functions whose molecular steps have not yet been fully described. Possible interaction partners described for the Mek-Erk-independent Raf activity have been Ask1, Bcl-2, Akt and Bag1 (Chen J et al., Proc Natl Acad Sci USA 2001, 98(14):7783-7788; Troppmair J et al., Biochem Pharmacol 2003, 66(8):1341-1345; Rapp U R et al., Biochim Biophys Acta 2004, 1644(2-3):149-158; Gotz R et al., Nat Neurosci 2005, 8(9):1169-1178). It is now assumed that both Mek-Erk-dependent and Mek-Erk-independent signal transduction mechanisms control the activation of upstream ras and Raf stimuli.
The isoenzymes of the phosphatidylinositol 3-kinases (PI3Ks) function primarily as lipid kinases and catalyse the D3 phosphorylation of second messenger lipids PtdIns (phosphatidylinositol) to PtdIns(3)P, PtdIns(3,4)P2, PtdIns(3,4,5)P3 phosphatidylinositol phosphates. PI3Ks of class I are composed in structural terms of catalytic subunit (p110alpha, beta, gamma, delta) and of regulatory subunit (p85alpha, beta or p101gamma). In addition, class II (PI3K-C2alpha, PI3K-C2beta) and class III (Vps34p) enzymes also belong to the family of PI3 kinases (Wymann M P et al., Biochim Biophys Acta 1998, 1436(1-2):127-150; Vanhaesebroeck B et al., Annu Rev Biochem 2001, 70:535-602). PIP rise induced by PI3Ks activates proliferative ras-Raf-Mek-Erk signaling pathway via the coupling of ras (Rodriguez-Viciaria P et al., Nature 1994, 370(6490):527-532) and stimulates the anti-apoptotic signaling pathway by recruiting Akt to the cell membrane and consequently overactivating this kinase (Alessi D R et al., EMBO J. 1996, 15(23):6541-6551; Chang H W et al., Science 1997, 276(5320):1848-1850; Moore S M et al., Cancer Res 1998, 58(22):5239-5247). Thus, activation of PI3Ks fulfils at least two crucial mechanisms of tumor development, specifically activation of cell growth and cell differentiation, and inhibition of apoptosis. In addition, PI3Ks also have protein-phosphorylating properties (Dhand R et al., EMBO J. 1994, 13(3):522-533; Bondeva T et al., Science 1998, 282(5387):293-296; Bondev A et al., Biol Chem 1999, 380(11):1337-1340; Vanhaesebroeck B et al., EMBO J. 1999, 18(5):1292-1302), which, for example, can induce serine autophosphorylation which intrinsically regulates PI3Ks. It is also known that PI3Ks have kinase-independent, regulating effector properties, for example in the control of heart contraction (Crackower M A et al., Cell 2002, 110(6):737-749; Patrucco E et al., Cell. 2004, 118(3):375-387). It has also been demonstrated that PI3 Kdelta and PI3 Kgamma are expressed specifically on haematopoietic cells and are thus potential points of attack for isoenzyme-specific PI3 Kdelta and PI3 Kgamma inhibitors in the treatment of inflammatory disorders, such as rheumatism, asthmas, allergies and in the treatment of B cell and T cell lymphomas (Okkenhaug K et al., Nat Rev Immunol 2003, 3(4):317-330; Ali K et al., Nature 2004, 431(7011): 1007-1011; Sujobert P et al., Blood 2005, 106(3):1063-1066). PI3Kalpha, which has recently been identified as a proto-oncogen (Shayesteh L et al., Nat Genet. 1999, 21(1):99-102; Ma Y Y et al., Oncogene 2000, 19(23):2739-2744; Samuels Y et al., Science 2004, 304(5670):554; Campbell I G, et al., Cancer Res 2004, 64(21):7678-7681; Levine D A et al., Clin Cancer Res 2005, 11(8):2875-2878) is an important target in the therapy of tumor disorders. The significance of the PI3K species as a target for active pharmaceutical ingredient (API) development is therefore extremely wide (Chang F et al., Leukemia 2003, 17(3):590-603).
Of equally great interest are PI3K-related kinases (PIKKs), which include serine/threonine kinases mTOR, ATM, ATR, h-SMG-1 and DNA-PK (Sabatini D M, Nat Rev Canc 2006, 6:729-34; Chiang G G et al., Methods Mol Biol 2004, 281:125-141). Their catalytic domains have a high sequence homology to the catalytic domains of PI3Ks.
Moreover, loss of tumor suppressor protein PTEN (Li J et al., Science 1997, 275(5308):1943-1947; Steck P A et al., Nat Genet. 1997, 15(4):356-362; Cully M et al., Nat Rev Canc 2006, 6:184-192)—whose function is the reversal of the phosphorylation initiated by PI3K—contributes to overactivation of Akt and its downstream cascade components and hence underlines the causal significance of PI3K as a target molecule for tumor therapy.
Various inhibitors of individual components of ras-Raf-Mek-Erk and PI3K-Akt signaling pathways have already been published and patented.
The current state of development in the field of the kinase-inhibitors, particularly of ras-Raf-Mek-Erk and of PI3K-Akt pathway, is detailed in the reviews by J. S. Sebolt-Leopold et al., Nat Rev Cancer 2004, 4(12):937-947; R. Wetzker et al., Curr Pharm Des 2004, 10(16):1915-1922; Z. A. Knight et al., Biochem Soc Trans. 2007, 35(Pt 2):245-9; R. A. Smith et al., Curr. Top. Med. Chem. 2006, 6, 1071-89; S. Faivre et al., Nat Rev Drug Discov 2006, 5, 671-688. Said publications contain a comprehensive list of published patent applications and patents which describe the synthesis and use of low molecular weight ras-Raf-Mek-Erk and PI3K inhibitors.
European Commission has granted marketing authorization to Nexavar® (sorafenib, Bay 43-9006; WO 99/32111, WO 03/068223 in July 2006 for the treatment of patients with advanced renal cell carcinoma who have failed prior interferon-alpha or interleukin-2 based therapy or are considered unsuitable for such therapy. Nexavar (Bay 43-9006) exhibits a relatively unspecific inhibition pattern of serine/threonine kinases and of tyrosine kinases, such as Raf, VEGFR2/3, Flt-3, PDGFR, c-Kit and further kinases. Great significance is attributed to this inhibitor in advanced tumor disorders induced by angiogenesis (for example in the case of kidney cell carcinoma) but also in the case of melanomas with high B-Raf mutation rate. The clinical action of Bay 43-9006 is currently also being determined in patients having refractory solid tumors in combination, for example, with docetaxel. To date, mild side effects and promising anti-tumor effects have been described. Inhibition of the kinases in the PI3K-Akt signaling pathway has neither been described nor disclosed for Bay 43-9006. Recent advances in the research and development of Raf Kinase inhibitors are described in a review of R. A. Smith et al., Curr. Top. Med. Chem. 2006, 6, 1071-89.
Mek1/2 inhibitor PD0325901 (WO 02/06213) is currently in phase II clinical trials for lung cancer and phase I/II clinical trials for the treatment of other solid tumors. The precursor substance CI-1040 (WO 00/35435, WO 00/37141) was noticeable by its high Mek specificity and target affinity. However, this compound was found to be metabolically unstable in phase I/II studies. Clinical data for the current successor substance PD0325901 are still to come. However, neither interaction with Erk1 or Erk2 nor a function inhibiting the PI3K-Akt signaling pathway or their simultaneous modulation has been published or disclosed for this Mek inhibitor.
A phase II study in malignant melanoma is under way for AZD-6244 (ARRY-142886), a selective MEK inhibitor from Array BioPharmaArray.
The PI3K/mTOR inhibitor BEZ-235 from Novartis (WO 06122806) entered a phase I clinical program as a targeted anticancer agent. The compound inhibited mTOR (IC50=21 nM), p110alpha, p110alpha E542K, p110alpha H107R and p110alpha E545K(IC50=4, 5, 18 and 4 nM, respectively) and p110beta, gamma and delta (IC50=76, 5 and 7 nM, respectively), while preserving selectivity over a panel of other kinases
Recent developments at Piramed have resulted in the synthesis of two series of compounds that act as phosphatidylinositol 3-kinase of class Ib (PI3K-Ib) inhibitors and are described as possessing potent anticancer activity. Additional indications include immune disorders, cardiovascular diseases, metabolism/endocrine disorders, neurodegenerative diseases and bacterial or viral infections (WO 06046035, WO 06046040).
Semafore recently initiated a phase I trial of its lead phosphoinositide 3-kinase (PI3K) inhibitor, SF-1126 (WO 04089925), in patients with solid tumor cancers. SF-1126 is a small-molecule conjugate containing a pan-PI3K inhibitor that selectively inhibits all PI3K class IA isoforms and other key members of the PI3K superfamily, including DNA PK and mTOR. Preclinically, SF-1126 has been shown to inhibit angiogenesis and cellular proliferation, induce apoptosis, block pro-survival signals and produce synergistic antitumor effects in combination with chemotherapy.
ICOS disclosed a PI3K inhibitor IC87114 with high PI3Kdelta isoenzyme specificity (WO 01/81346). For PI103 (WO 04/017950).
Exelixis has submitted an IND for XL-147, a novel anticancer compound. XL-147 is an orally available small-molecule inhibitor of phosphoinositide-3 kinase (PI3K). Inactivation of PI3K has been shown to inhibit growth and induce apoptosis in tumor cells. In preclinical studies, XL-147 slowed tumor growth or caused tumor shrinkage in multiple preclinical cancer models, including breast, lung, ovarian and prostate cancers, and gliomas.
Moreover, a highly noted field of research exists in the early development of PI3K inhibitors (see reviews of Z. A. Knight et al., Biochem Soc Trans. 2007, 35(Pt 2):245-9; R. Wetzker et al., Curr Pharm Des 2004, 10(16):1915-19222004).
Inhibitors of SAPK signaling pathway, either of Jnk or of p38, are described in the literature (Gum R J et al., J Biol Chem 1998, 273(25):15605-15610; Bennett B L et al., Proc Natl Acad Sci USA. 2001, 98(24):13681-13686; Davies S P et al., Biochem J. 2000, 351(Pt 1):95-105). However, no function of inhibiting the PI3Ks nor any specific inhibition of Erk1 or Erk2 or else any specific inhibition of SAPKs, Erk1, Erk2, or PI3Ks has been disclosed for these SAPK inhibitors.
6- or 7-substituted pyrido[2,3-b]pyrazine derivatives find wide use in pharmaceutical chemistry as pharmacologically active compounds and as synthetic units.
Patent applications WO 04/104002 and WO 04/104003, for example, describe pyrido[2,3-b]pyrazines which may be 6- or 7-substituted by urea, thiourea, amidine or guanidine groups. These compounds have properties as inhibitors or modulators of kinases, especially of tyrosine and serine/threonine kinases. The use as a medicament is reported. In contrast, use of these compounds as modulators of lipid kinases, alone or in combination with tyrosine and serine/threonine kinases, has not been described.
Moreover, WO 99/17759 describes pyrido[2,3-b]pyrazines which bear, in 6-position, inter alia, alkyl-, aryl- and heteroaryl-substituted carbamates. These compounds are intended to be used for the modulation of serine-threonine protein kinase function.
Patent application WO 05/007099 describes, inter alia, urea-substituted pyrido[2,3-b]pyrazines as inhibitors of serine/threonine kinase PKB. However, the document does not further define the R radical, which describes the range of possible substitutions on urea. Therefore, the range of possible substitution on urea is thus not clearly disclosed. As for these compounds, use in the treatment of cancer disorders is reported. However, no specific examples of urea-substituted pyridopyrazines having the claimed biological properties are given. In addition, the pyridopyrazines described here differ significantly in structure from the novel pyrido[2,3-b]pyrazines described in this invention.
Further examples of 6- and 7-urea-substituted pyrido[2,3-b]pyrazines are reported in WO 05/056547. However, the compounds disclosed there have additional carbonyl, sulphoxy, sulphone or imine substitution in the 2- or 3-position, which means that the compounds differ structurally significantly from the novel pyrido[2,3-b]pyrazines described in this invention. The pyridopyrazines reported in WO 05/056547 are described as inhibitors of protein kinases, especially of GSK-3, Syk and JAK-3. Uses reported include use in the treatment of proliferative disorders. Use of these compounds as modulators of lipid kinases, alone or in combination with serine/threonine kinases, is not described.
WO 04/005472 describes, inter alia, 6-carbamate-substituted pyrido[2,3-b]pyrazines which, as antibacterial substances, inhibit the growth of bacteria. Antitumor action is not described.
Certain diphenylquinoxalines and -pyrido[2,3-b]pyrazines with specific alkylpyrrolidine, alkylpiperidine or alkylsulphonamide radicals on a phenyl ring, which may additionally also bear urea or carbamate substitutions in 6- or 7-position, are described in patent applications WO 03/084473, WO 03/086394 and WO 03/086403 as inhibitors of serine/threonine kinase Akt. For these compounds, use in the treatment of cancer disorders is reported. For pyrido[2,3-b]pyrazine example compounds described there, no defined indication of biological action is specified. Moreover, there is a significant structural difference to the novel pyrido[2,3-b]pyrazines described in this invention.
Moreover, patent application WO 03/024448 describes amide- and acrylamide-substituted pyrido[2,3-b]pyrazines which also contain carbamates as additional substitutents and can be used as histone deacetylase inhibitors for the treatment of cell proliferation disorders.
A further publication (Temple, C. Jr.; J. Med. Chem. 1990:3044-3050) exemplarily describes the synthesis of a 6-ethyl carbamate-substituted pyrido[2,3-b]pyrazine derivative. Antitumor action is neither disclosed nor rendered obvious.
The synthesis of further derivatives of 6-ethyl carbamate-substituted pyrido[2,3-b]pyrazine is described in a publication by R. D. Elliott (Elliott R D, J. Org. Chem. 1968: 2393-2397). Biological action of these compounds is neither described nor rendered obvious.
The publication by C. Temple (Temple, C. Jr., J. Med. Chem. 1968:1216-1218) describes the synthesis and examination of 6-ethyl carbamate-substituted pyrido[2,3-b]pyrazines as potential active antimalarial ingredients. Antitumor action is neither disclosed nor rendered obvious.
WO 2005/021513 is directed to the preparation of condensed n-pyrazinyl-sulfonamides and their use in the treatment of chemokine mediated diseases. Antitumor action is neither disclosed nor rendered obvious.
JP 2006137723 describes the preparation of sulfonamides, their use as CCL17 and/or 22 regulators, and pharmaceuticals containing them for treatment of the chemokine-associated diseases. Antitumor action is neither disclosed nor rendered obvious.
Sako M. (Sako M., Houben-Weyl, Science of Synthesis 2004, 16.20:1269-1290) gives a general overview about the synthesis of pyridopyrazines. Antitumor action is neither disclosed nor rendered obvious.
U.S. Pat. No. 4,082,845 discloses 3-(1-piperazinyl)-pyrido[2,3-b]pyrazines. Antitumor action is neither disclosed nor rendered obvious.
WO 04/005472 relates to antibacterial inhibitors of Ftsz protein. Pyridopyrazines are not explicitly mentioned. Antitumor action is neither disclosed nor rendered obvious.
WO 02/090355 describes the preparation of N-aroyl cyclic amines as orexin antagonists. Pyrido[2,3-b]pyrazines are not mentioned.
JP 50053394 discloses 3-substituted 5-alkyl-5,8-dihydro-8-oxopyrido[2,3-b]pyrazine-7-carboxylic acids and their esters. Antitumor action is neither disclosed nor rendered obvious.
U.S. Pat. No. 3,209,004 relates to 3,6-diamino—N-(2,2-dialkoxyethyl)pyrido[2,3-b]pyrazine-2-carboxamides. Antitumor action is neither disclosed nor rendered obvious.
U.S. Pat. No. 3,180,868 describes 3,6-diamino—N-(substituted)pyrido[2,3-b]pyrazine-2-carboxamides. Antitumor action is neither disclosed nor rendered obvious.
Chen J J et al. (Chen J J et al., J. Am. Chem. Soc. 1996, 118:8953-8954) discuss the synthesis of pyrido[2,3-b]pyrazines from pyrazine C-nucleosides. Antitumor action is neither disclosed nor rendered obvious.
Nagel A et al. (Nagel A et al., J. Heterocyclic Chem. 1979, 16:301-304) show NMR data of pyrido[2,3-b]pyrazine derivatives. Antitumor action is neither disclosed nor rendered obvious.
Tanaka T et al. (Tanaka T et al., Yakugaku Zasshi 1975, 95(9):1092-1097) describe the synthesis of certain pyrido[2,3-b]pyrazine derivatives. Antitumor action is neither disclosed nor rendered obvious.
Osdene T S et al. (Osdene T S et al., J. Chem. Soc. 1955, pp. 2032-2035) discuss the synthesis of 3,6-diaminopyridopyrazine and derived compounds with potential anti-folic acid activity. Antitumor action is neither disclosed nor rendered obvious.
WO 2006/128172 is directed to a method for treating B cell regulated autoimmune disorders. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
WO 2006/091395 relates to inhibitors of serine/threonine kinase Akt activity. Pyrido[2,3-b]pyrazine derivatives are comprised. However, possible pyrido[2,3-b]pyrazine derivatives are substituted with substituted phenyl and (C3-C8)cycloalkyl, aryl, heteroaryl and heterocyclyl.
WO 06/081179, WO 06/017326, WO 06/017468, WO 06/014580, WO 06/012396, WO 06/002047 and WO 06/020561 are all directed to antibacterial agents. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
WO 2006/074147 discloses 4-arylamino-quinazolines as activatots of caspases and inducers of apoptosis. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
WO 2006/024666 relates to the preparation of pyridine methylene thioxothiazolidinones as phosphoinositide inhibitors. Pyrido[2,3-b]pyrazine derivatives are comprised. However, the displayed pyrido[2,3-b]pyrazine derivatives are not substituted at their pyrazine moiety.
WO 06/021448 is directed to compounds with antibacterial action. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
WO 2005/123733 describes pyrido[2,3-b]pyrazine derivatives as agents for combatting phytopathogenic fungi. However, possible pyrido[2,3-b]pyrazine derivatives are substituted with aryl, heteraryl, halogen or substituted amino at their pyridine moiety.
WO 2005/123698 describes agents for combatting phytopathogenic fungi. Pyrido[2,3-b]pyrazine derivatives are comprised. However, the comprised pyrido[2,3-b]pyrazine derivatives are substituted with aryl, heteraryl, halogen or substituted amino at their pyridine moiety.
US 2005/0272736 relates to tri- and bi-cyclic heteroaryl histamine-3 receptor ligands. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
US 2005/0272728 discloses bicyclic amines bearing heterocyclic substituents as H3 receptor ligands. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
US 2005/0256309 relates to tri- and bi-cyclic heteroaryl histamine-3 receptor ligands. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
US 2005/0256118 discloses bicyclic amines bearing heterocyclic substituents as H3 receptor ligands. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
US 2005/0165028 is directed to N-heteroaryl substituted benzamides as vanilloid receptor ligands. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
WO 05/023807 describes bicyclic quinazolin-4-ylamine derivatives as capsaicin receptor modulators. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
EP 1661889, which corresponds to WO 2005/07099, relates to pyridinyl benzene-sulfonylamide derivatives as chemokine receptor antagonist. Pyrido[2,3-b]pyrazine derivatives are comprised. However, the comprised pyrido[2,3-b]pyrazine derivatives are concomitantly substituted with sulfonamides and cyclic structures.
WO 04/055003 discloses quinazolin-4-yl)amines as capsaicin receptor modulators. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
US 2004/0092521 discloses bicyclic amines bearing heterocyclic substituents as H3 receptor ligands. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
WO 2004/030635 is directed to vasculostatic agents. Pyrido[2,3-b]pyrazine derivatives are comprised. However, the comprised pyrido[2,3-b]pyrazine derivatives are substituted with aryl or heteraryl at their pyrazine moiety.
WO 03/064421 describes aminopiperidine derivatives as antibacterial agents. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
WO 03/064431 also describes aminopiperidine derivatives as antibacterial agents. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
WO 02/055079 relates to 8-hydroxy-1,6-naphthyridine-7-carboxamides as inhibitors of HIV integrase and HIV replication. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
WO 00/12497 discloses quinazoline derivatives as TGF-beta and p38-alpha kinase inhibitors. However, pyrido[2,3-b]pyrazines are not disclosed.
WO 99/43681 is directed to N-(4-piperidinylmethyl)thieno[3,2-b]pyridin-7-amines and related compounds as GABA brain receptor ligands. Pyrido[2,3-b]pyrazines are not disclosed. Antitumor action is neither disclosed nor rendered obvious.
WO 95/15758 describes aryl and heteroaryl quinazoline compounds which inhibit CSF-1R receptor tyrosine kinase. Pyrido[2,3-b]pyrazines are not disclosed.
U.S. Pat. No. 5,480,883 describes bis mono- and bicyclic aryl and heteroaryl compounds which inhibit EGF and/or PDGF receptor tyrosine kinase. Pyrido[2,3-b]pyrazine derivatives are comprised. However, the comprised pyrido[2,3-b]pyrazine derivatives are directly substituted with aryl or heteraryl at their pyrazine moiety.
WO 2006/059103 relates to substituted pyridines and derivatives thereof. Pyrido[2,3-b]pyrazines are not disclosed.
WO 2007/023186 discloses pyrazine derivatives and their use as PI3K inhibitors. Pyrido[2,3-b]pyrazine derivatives are comprised. However, the comprised pyrido[2,3-b]pyrazine derivatives are directly substituted with sulfonamides at their pyrazine moiety.
WO 2007/044729 also describes pyrazine derivatives and their use as PI3K inhibitors. Pyrido[2,3-b]pyrazine derivatives are comprised. However, the comprised pyrido[2,3-b]pyrazine derivatives are directly substituted with sulfonamides at their pyrazine moiety.
WO 2004/108702 is directed to indole derivatives. Pyrido[2,3-b]pyrazine derivatives are comprised. However, the comprised pyrido[2,3-b]pyrazine derivatives are directly substituted with glyoxyl-indolyl at their pyrimidine moiety.